1. Field of the Invention
The present invention relates to a centrifugal separator, and more particularly to structure for facilitating the opening and closing of a door for sealing a rotor-housed rotor chamber.
2. Description of the Related Art
In a centrifugal separator, a rotor on which a sample to be separated is supported via a tube and a bottle is held in a rotor chamber (rotary chamber), and the rotor is rotated at a high speed by a driving unit, such as a motor with an opening of the rotor chamber closed tightly with a door, the separation and the refining of the sample supported on the rotor being thereby done. The rotational speed of the rotor differs depending upon the use of a separated or refined product. Products having a wide range of rotational frequencies from a comparatively low maximum level of around several thousands (rpm) to a high maximum level of around one hundred and fifty thousands (rpm) are generally provided.
When the rotor of the centrifugal separator is rotated at a high speed in the rotor chamber closed tightly with the door, frictional heat occurs between the rotor and the air existing in the rotor chamber, to cause a windage loss to be brought about, so that the temperature of the rotor increases to an abnormal level. Therefore, many centrifugal separators rotated at a high speed of, for example, not smaller than twenty thousands rpm are mounted with cooling units. On a high-speed or super high-speed centrifugal separator, a vacuum unit for reducing the pressure of the interior of the rotor chamber to a high vacuum or a low vacuum is mounted in addition to the above-mentioned cooling unit. The mounting of the vacuum unit serves as techniques for practicing the more complete prevention of a temperature rise ascribed to the windage loss.
A cooling unit-carrying centrifugal separator is provided with a cooler made of refrigerating pipes extending along an inner circumferential surface of a rotor-holding chamber as shown, for example, in JP-A-2002-336738. This cooler makes the rotor chamber cool, suppresses the generation of heat occurring due to the rotation of the rotor, and thereby controls the rotor temperature to be at not higher than a predetermined level. Therefore, it is demanded in the related art centrifugal separator that the interior of the rotor chamber closed tightly with the door and the outside thereof be thermally shut off from each other, and that the degree of closure of the space (closed chamber) defined by and sealed with wall members of the rotor chamber and door against the outside air is improved.
The rotor chamber is made as a space closed against the outside except the opening portion thereof which is provided with the door used when the rotor and sample are inserted and withdrawn thereinto and therefrom. Furthermore, a packing made of an elastic member is provided between the rotor chamber and door. When the door is closed, the packing is pressed so that the outside air does not enter the rotor chamber, and thus a space closed with the rotor chamber and door is formed. The “closed space” or “sealed space” used in the specification of the present invention means usually a space defined by wall members which permit such a little leakage of a small quantity of the air that does not have influence upon the cooling capacity of the space. Such a space may, of course, be a space thermally shut off from or defined with respect to the outside air more completely by using a vacuum seal.
An example of a centrifugal separator mounted with a vacuum pump for making the interior of a rotor chamber vacuous in order to reduce a windage loss to as great an extent as possible of a high-speed rotated rotor is disclosed in JP-A-9-75782. In the techniques disclosed in JP-A-9-75782, a door is closed so as to seal an opening of the rotor chamber off the outside air, and an air leakage valve for communicating the interior of the rotor chamber and the outside air with each other is then closed to make the rotor chamber highly vacuous. The rotor is rotated in this condition at a high speed. After the operation finishes being carried out, the rotor is taken out from the rotor chamber by opening the air leakage valve by using a special switch to open the rotor chamber into the atmospheric air, and thereafter opening the door. Especially, the characteristics of this centrifugal separator reside in that the switch controlled by both a valve-opening signal and a rotational frequency detecting signal is provided so as to prevent the air leakage valve from being opened inadvertently by an erroneous operation during the rotation of the rotor.